JPH1025296A - Fibrous compound and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new fibrous compound belonging to a monoclinic crystal system having each specific lattice constants, having a composition shown by the chemical formula C3 N6 H12 B2 O6 as single crystal, and useful as an intermediate for hexagonal boron nitride and the crystallite grains of the boron nitride. SOLUTION: This new fibrous compound has crystal structure shown by the formula and, belongs to a monoclinic crystal system virtually having lattice constants as follows: (a)=3.600Å, (b)=20.143Å, (c)=14.121Å, and β=92.11 deg., and has a composition shown by the chemical formula C3 N6 H12 B2 O6 as single crystal. This compound is excellent in such properties as thermal conductivity, electrical insulation, heat resistance, corrosion resistance, chemical stability and lubricity and used as an intermediate for hexagonal boron nitride (h-BN) useful as an electrical insulation material, releasant, abrasive or thermal conductivity-imparting agent, and for the crystallite grains of the boron nitride. This fibrous compound is obtained by the following process: a melamine-based compound is reacted with boric acid or boron oxide in an appropriate solvent under heating, and then, crystal is grown during cooling the reaction product, and the deposited crystal is filtered and then rapidly dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fibrous compound having a novel chemical formula of C ₃ N ₆ H ₁₂ B ₂ O _{6 which} is useful as a raw material for boron nitride and a method for producing the same. The fibrous compound of the present invention is useful as an intermediate of hexagonal boron nitride (hereinafter referred to as h-BN) and further, fine crystal particles of boron nitride. Boron nitride is an insulating material, release agent, abrasive,
It is useful as a thermal conductivity imparting agent.

[0002]

2. Description of the Related Art Boron nitride has thermal conductivity, electrical insulation,
It is known as a compound having excellent properties such as heat resistance, corrosion resistance, chemical stability, and lubricity, and its use is being actively developed. In recent years, its heat resistance and heat dissipation properties have attracted attention in the field of electric and electronic members, and further application development is expected.

[0003]

Conventionally, there are known industrial methods for producing boron nitride, which include 1) a method of reducing and nitriding boron oxide, 2) a method of nitriding simple boron, and 3) a method of reducing and nitriding boron halide. Have been. Since h-BN obtained by these manufacturing methods has a scale-like shape derived from the manufacturing method, when a sintered body is manufactured or composited with other ceramics, or when used as a composite material, there are restrictions from the shape. Is receiving. On the other hand, JP-A-60-1
No. 51202 discloses a method for producing boron nitride. The publication discloses that a boron atom and a nitrogen atom coexist in advance from one or more boron compounds selected from boric acid and a metal salt of boric acid, and one or more nitrogen-containing compounds that can be combined with the boron compound. (This compound is considered to be a mixture of an amorphous C—H—N—B—O-based compound and a nitrogen or boron source compound), and then the compound is inert gas or reducing compound. By heating to 600 ° C. or more in a gas atmosphere, scaly, columnar, and needle-shaped boron nitride is obtained. However, the fiber length of the fibrous boron nitride obtained by this method is at most 20 μm, and when it is used as a thermal conductivity improving material, the size is still not sufficiently satisfactory. Further, in this method, a fibrous boron nitride precursor could not be obtained in an aqueous solvent. The object of the present invention is to
h-BN, further chemical formula _{C 3 N 6 H 12 B 2} O 6 having a useful novel compositions as intermediates boron nitride microcrystal grains
To provide a fibrous compound represented by the formula:

[0004]

According to the present invention, substantially, the lattice constants a = 3.600 °, b = 20.143 °, and c = 14.1.
21 °, β = 92.11 °, belonging to the monoclinic system,
The present invention relates to a fibrous compound having a chemical formula of C ₃ N ₆ H ₁₂ B ₂ O ₆ which is a single crystal. Further, the present invention, a melamine compound and boric acid or boron oxide is heated and reacted in a suitable solvent,
Upon cooling to grow crystals, it was filtered off the precipitated fibrous compound formula C _3, characterized in that rapid drying N ₆ H ₁₂ B
_{The present} invention relates to a method for producing a fibrous compound having a composition of ₂ O ₆ .

[0005]

DETAILED DESCRIPTION OF THE INVENTION The chemical formula of the present invention, C ₃ N ₆ H ₁₂ B ₂ O ₆
A fibrous compound having a composition of substantially has a lattice constant a =
3.600 °, b = 20.143 °, c = 14.121
新 規, β = 92.11 °, a novel compound having a single crystal structure belonging to a monoclinic system and not described in any literature. According to the single crystal automatic X-ray structure analysis, the crystal structure of the compound of the present invention is as follows.

[0006]

Embedded image

This compound is useful as an intermediate between boron nitride and various boron nitride compounds. It may contain a small amount of a compound other than the above crystal structure. The fibrous compound having the composition of the chemical formula C ₃ N ₆ H ₁₂ B ₂ O ₆ of the present invention can have an average fiber length of about 30 μm to about 5 mm depending on the reaction conditions. This has an average aspect ratio of about 10 to 50. Chemical formula C ₃ N ₆ H of the present invention
_The fibrous compound having the composition of ₁₂ B ₂ O ₆ is obtained by heating and reacting a melamine compound with boric acid or boron oxide in an appropriate solvent, growing crystals upon cooling, and filtering out the precipitated fibrous compound. Can be obtained by rapid drying.

As the melamine compound, compounds having an NH ₂ group such as melamine, ammeline, ammelide, melam, melon and the like can be used. As boric acid, orthoboric acid, metaboric acid, tetraboric acid and the like can be used, and as boron oxide, diboron trioxide, diboron dioxide, tetraboron trioxide, tetraboron pentoxide and the like can be used. Boric acid or boron oxide and melamine-based compound alone or simultaneously heated in a solvent,
After completely dissolving boric acid or boron oxide and the melamine compound, 2 mol of boric acid per 1 mol of the melamine compound forms molecular crystals by hydrogen bonding with the crystal precipitation in the cooling process, and the compound is formed. The compound of the present invention can be obtained by the crystal growth of When the boric acid and the melamine compound are dissolved alone, it is necessary to mix the boric acid solution and the melamine compound solution in order to obtain the compound of the present invention. It is preferable to mix a predetermined amount so that the molar ratio of the system compound becomes 2/1. Although it is possible to obtain the compound of the present invention also in the case of excess boric acid or melamine-based compound,
When boric acid or melamine compound having a solubility equal to or higher than the solubility at the time of cooling is dissolved, it is re-precipitated as each crystal (particulate), and the product of the present invention obtained after filtration and rapid drying is a fibrous compound. And a mixture of particles. The melamine-based compound decomposes and disappears during the heat treatment for forming h-BN, but boric acid remains as an impurity for the compound of the present invention which is considered to be particulate h-BN or oxynitride. Further, it is preferable as an embodiment of the present invention to carry out the dissolution of a predetermined amount calculated from the viewpoint of effective utilization of the raw material.

In the present invention, the reaction mechanism is not clear, but the addition reaction of boric acid and melamine by heating is an essential requirement. Then, upon cooling from the reaction temperature, crystal growth occurs and the compound of the present invention can be obtained. Also,
As a feature of the present invention, the fiber length of the obtained compound can be controlled by setting the reaction temperature. μm
In order to obtain the compound of the present invention having a fiber length on the order of, the reaction temperature below the boiling point of the solvent, in order to obtain the compound of the present invention having a fiber length on the order of mm, from the boiling point of the solvent to
The synthesis is preferably performed at a reaction temperature of 200 ° C. If the heating temperature is lower than 60 ° C., the fiber length of the obtained compound becomes short, and the production efficiency is undesirably reduced. At a temperature of 200 ° C. or higher in hydrothermal synthesis, an increase in equipment cost and coarsening (abnormal growth) of the obtained crystalline compound are likely to occur, and the temperature is preferably 200 ° C. or lower from the viewpoint of stable production. The reaction time at the set temperature is not particularly limited, but complete dissolution of the raw materials is a preferable requirement for practicing the present invention. If the cooling rate is too rapid, the growth of the fiber and the crystallinity of the fiber are adversely affected, and if the cooling rate is too slow, the productivity deteriorates. Therefore, a setting within a range that does not hinder the use of the present compound as a raw material is appropriately selected. Is preferred. The obtained crystals are separated from the solvent by a usual filtration treatment. Furthermore, as compared with the prior art, according to the production method of the present invention, it is possible to obtain an acicular compound even when the solvent is completely aqueous.

Next, what is important in the embodiment of the present invention is as follows.
The shape of the obtained fibrous present compound is
In order to obtain a dry product as it is, vacuum drying and reduction
Performing rapid drying such as pressure drying. Solvent drying
Setting up to what level the limit value of the drying speed can be handled
Cannot be specified due to drying temperature, dryer capacity, etc.
However, the quicker the drying, the better the shape retention.
If the drying speed is too slow and it is heated,
The phenomenon considered to be re-melting of the needle crystals
A collapsed amorphous C—H—N—B—O-based compound is obtained,
Not good. That is, the present invention relates to boric acid or boron oxide,
The melamine compound is dissolved under heating, and the addition reaction is started.
At the time of cooling precipitation to form a fibrous form with crystal growth in the a-axis direction,
Drying is obtained as a single crystal compound by rapid drying.
It was found that it was completed. In addition,
As a compound similar to the light compound, the compound of formula C
_ThreeN₆H₁₂B_Two0₆XH_TwoO (0 <x <6)
Dehydrated C_ThreeN₆H₁₂−_2xB_TwoO_6-xCompound is obtained
In some cases, this compound also retains its fiber shape.
Enclosed in the present invention. The crystallinity of the precursor compound
Being good is for applications such as ceramics sintered compacts
When used for
It is known that the compounds of the present invention are industrially useful
It is a compound.

[0011]

EXAMPLES The fibrous compound of the present invention will be described in detail below with reference to examples. Example 1 400 g of deionized water was placed in a 500 ml glass beaker, 12 g of melamine was added thereto, and the mixture was stirred for 80 minutes.
℃ to dissolve completely, and add orthoboric acid 1
After adding 5 g, dissolving uniformly and reacting, the mixture is gradually cooled to room temperature to produce a fibrous compound.
Vacuum dried at 50 ° C. 24 g of the obtained fibrous compound
The average fiber length is 60 μm, CHN analysis, B analysis by high frequency inductively coupled plasma emission spectrometry (ICP), and an automatic single crystal X-ray structure analyzer (AFC / RASA-
7R, manufactured by Rigaku Denki Co., Ltd.), it was confirmed that this compound belongs to a monoclinic system and has a composition of C ₃ N ₆ H ₁₂ B ₂ O ₆ in which 2 mol of boric acid is added to 1 mol of melamine. . In addition, it was a single crystal according to the result of TEM electron diffraction. FIG. 1 shows a scanning electron microscope (SEM) photograph of the obtained fibrous compound, FIG. 2 shows a transmission electron microscope (TEM) photograph thereof, and FIG.
FIG. 4 shows a TEM electron beam diffraction photograph, FIG. 4 shows an X-ray diffraction (XRD) chart, and FIG. 5 shows a schematic diagram showing a crystal structure by an automatic single crystal X-ray structure analysis.

Example 2 400 ml of deionized water, 6 g of melamine, 7.5 orthoboric acid
It carried out similarly to Example 1 using g. The obtained fibrous compound was 11 g, and the average fiber length was 80 μm. Similarly, as a result of analysis, the same compound as in Example 1 was obtained. Example 3 Synthesis was carried out using 30 g of melamine in the same manner as in Example 1,
38 g of the compound obtained after vacuum drying was a mixture of fibrous and particulate. As a result of XRD analysis and SEM observation, a mixture of particulate melamine reprecipitated crystals was obtained in addition to the fibrous compound of the present invention. Example 4 The same synthesis as in Example 1 was performed using 12 g of melamine and 30 g of orthoboric acid. The product obtained after vacuum drying is 3
It was 0 g, and was a mixture of fibrous and particulate. As a result of XRD analysis and SEM observation, this mixture was found to contain a particulate reprecipitated crystal boric acid in addition to the fibrous compound of the present invention.

Example 5 Synthesis was carried out at the reaction temperature of 60 ° C., using the same raw materials as in Example 1, and as a result, the obtained product was in the form of fibrous C ₃ N ₆ H ₁₂ B _2.
A single crystal compound having a composition of O ₆ and an average fiber length of 30
μm. Example 6 As a boron source, 9 g of boron oxide was used instead of orthoboric acid.
As a result of performing the same reaction as in Example 1 except that
3 g of a compound with an average fiber length of 60 μm were obtained. As a result of analysis, this compound was the same as Example 1. Example 7 250 ml of deionized water, 12 g of melamine, orthoboric acid 1
5 g was dissolved and reacted at 120 ° C. in an autoclave, gradually cooled to room temperature, and the precipitated fibrous compound was separated by filtration and dried at 50 ° C. in vacuo. From SEM observation, 24 g was obtained as a fibrous compound having an average fiber length of 1 to 2 mm. The same analysis as in Example 1 was carried out, and the result was the same compound as in Example 1. FIG. 6 shows an SEM photograph of the obtained fibrous compound, and FIG. 7 shows an XRD diffraction chart thereof. Example 8 As a result of performing the same reaction as in Example 7 at a reaction temperature of 180 ° C., the average fiber length of the obtained fibrous compound was 2 to 4 mm from SEM observation.

Example 9 4 g of melamine, 5 g of orthoboric acid and 200 ml of methanol were placed in a separable flask equipped with a condenser and completely dissolved in an oil bath at 80 ° C. under reflux. After separating, it was vacuum dried at 50 ° C. The obtained compound was found to have an average fiber length of 40 μm by SEM observation.
m and the same analysis as in Example 1 was carried out. As a result, the compound was the same as that in Example 1. Example 10 The same reaction as in Example 9 was carried out except that acetone was used instead of methanol as a solvent. As a result, the obtained compound was the same as Example 1 with an average fiber length of 35 μm.

Comparative Example 1 12 g of melamine and 15 g of orthoboric acid were placed in a 500 ml beaker together with 400 ml of deionized water,
After stirring reaction for an hour, the mixture was separated by filtration and dried at 105 ° C. The obtained compound was scaly with an average fiber length of 5 μm, and was amorphous by XRD analysis. FIG. 8 shows an SEM photograph of the obtained fibrous compound. Reference Example 1 The fibrous precursor compound obtained in Example 1 was subjected to a heat treatment at 1400 ° C. for 1 hour in a nitrogen atmosphere. The obtained compound was a single compound of h-BN from XRD analysis,
M observation confirmed that the fibrous material had an average length of 60 μm and the shape of the precursor was maintained. FIG. 9 shows an SEM photograph of the obtained fibrous compound.

[0016]

According to the present invention, a fiber represented by the chemical formula C ₃ N ₆ H ₁₂ B ₂ O ₆ having a novel composition useful as an intermediate of h-BN and also fine crystal grains of boron nitride. Compound can be obtained.

[Brief description of the drawings]

FIG. 1 is an SEM photograph showing the shape of a fibrous compound obtained in Example 1.

FIG. 2 is a TEM photograph showing the shape of the fibrous compound obtained in Example 1.

FIG. 3 is a TEM electron diffraction photograph of the fibrous compound obtained in Example 1.

FIG. 4 is an XRD diffraction chart of the fibrous compound obtained in Example 1.

FIG. 5 is a schematic diagram showing a crystal structure of the fibrous compound obtained in Example 1 by single crystal automatic X-ray structure analysis.

FIG. 6 is an SEM photograph showing the shape of the fibrous compound obtained in Example 7.

FIG. 7 is an XRD diffraction chart of the fibrous compound obtained in Example 7.

FIG. 8 is an SEM photograph showing the shape of the fibrous compound obtained in Comparative Example 1.

FIG. 9 is an SEM photograph showing the shape of the fibrous compound obtained in Reference Example 1.

Claims (8)

[Claims] 1. Substantially lattice constant a = 3.600 °, b
= 20.143 °, c = 14.121 °, β = 92.11
° C, which belongs to the monoclinic system and is a single crystal of the formula C ₃
A fibrous compound having a composition of N ₆ H ₁₂ B ₂ O ₆ . _2. A fibrous compound having a composition of the chemical formula C ₃ N ₆ H ₁₂ B ₂ O ₆ having an average length of 30 μm or more and 5 mm or less. 3. A melamine compound and boric acid or boron oxide are heated and reacted in a suitable solvent to grow crystals upon cooling, and the precipitated fibrous compound is filtered off and rapidly dried. A method for producing a fibrous compound having a composition of the chemical formula C ₃ N ₆ H ₁₂ B ₂ O ₆ . 4. The raw material is completely dissolved in a solvent.
The manufacturing method as described. 5. The method according to claim 3, wherein the solvent is aqueous. 6. The process according to claim 3, wherein the reaction temperature is from 60 ° C. to the boiling point of the solvent. 7. The method according to claim 3, wherein the reaction is carried out in a closed vessel, and the reaction temperature is not lower than the boiling point of the solvent and not higher than 200 ° C. 8. The production method according to claim 3, wherein rapid drying is performed by vacuum drying or vacuum drying.